The Theory of Plate Tectonics

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Vocabulary

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Plates: parts of the lithosphere that have broken up into sections
Scientific theory: a well tested concept that explains a wide range of observations
Plate tectonics: a theory that states pieces of Earth's lithosphere are in constant slow motion driven by convection currents in the mantle
Faults: breaks in Earth's crust where where rocks have slipped past each other
Transform boundary: a place where two plates slip past each other moving in opposite directions
Divergent boundary: a place where two plates move apart or diverge
---Rift valley:a deep valley that forms along the divergent boundary
Convergent Boundary: a place where two plates come together or converge

Outline

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A Theory of Plate Motion

• J. Tuzo Wilson combined what geologists knew about Sea-Floor Spreading, Earth's plates, and the continental drift into a single theory, the theory of plate tectonics
  • The theory of plate tectonics explains the formation, movement, and subduction of Earth's plates

Plate Boundaries

• There are three kinds of boundaries
  • Transform boundaries
  • Divergent boundaries
  • Convergent boundaries

The Continent's Slow Dance

• the plates move very slowly( 1 to 10 centimeters a year)
  • North American and Eurasian plates are floating apart at a rate of 2.5 centimeters a year( as fast as your fingernails grow)

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